1. Field of the Invention
The present invention relates to a positive temperature coefficient (PTC) heater, and more particularly, to a PTC heater in which a PTC rod and a heat-radiating fin are joined together by soldering, thereby improving a coupling force and heat transfer efficiency, increasing durability due to the improved coupling force, making it possible to remove side frames as well as a cover of the heat-radiating fin to reduce material cost and weight, particularly in which the soldering is performed in a relative low-temperature state using a tin solder, thereby preventing characteristics of a PTC element from being varied during the soldering, and thus smoothly exerting performance of the PTC element.
2. Description of Related Art
A vehicle is equipped with an air conditioning system for selectively supplying cold and warm air to the inside thereof. In the summer season, an air conditioner is actuated to supply the cold air. In the winter season, a heater is actuated to supply the warm air.
In general, the heater is based on a heating system in which a coolant heated by circulating through an engine exchanges heat with air introduced by a fan, so that warmed air is supplied to the inside of the vehicle. This heating system has high energy efficiency because it uses the heat generated from the engine.
However, in the winter season, it takes some time until the engine is heated after starting. Thus, after starting, the heating is not immediately performed. As such, for the heating, the engine often idles for a predetermined time prior to moving the vehicle until the engine is heated to raise the temperature of the coolant. This idling of the engine causes energy consumption and environmental pollution.
In order to prevent this problem, a use has been made of a method of heating the interior of the vehicle using a separate pre-heater for a predetermined time when the engine is being warmed up. A conventional heater using a heating coil effectively performs the heating due to a high quantity of heat, but its parts are frequently repaired and exchanged due to a short lifetime of the heating coil.
Thus, a heater using a positive temperature coefficient (PTC) element has recently been developed. This PTC heater has low fire danger, and can guarantee semi-permanent use due to a long lifetime. For this reason, the coverage of the PTC heater becomes very wide. Further, the PTC heater used for the pre-heater by nature generally has a relatively small capacity. Recently, there has been a tendency to develop a high capacity of PTC heater due to diversification of the vehicle and user's demand.
FIGS. 1 and 2 are schematic exploded perspective views illustrating the structure of an exemplary PTC heater.
As illustrated in FIGS. 1 and 2, the PTC heater generally includes a plurality of PTC rods 10, each of which has a built-in PTC element and an anode terminal 11 protruding from one end thereof and is electrically heated to generate heat, heat-radiating fin modules 20, which are coupled in close contact with opposite sides of the respective PTC rods 10 in pairs, cathode terminals 30 disposed in parallel between the neighboring heat-radiating fin modules 20, and upper and lower housings 40 and 50 coupled to opposite longitudinal ends of the PTC rods 10.
At this time, in order to allow the PTC rods 10, heat-radiating fin modules 20 and cathode terminals 30, all of which are disposed parallel to one another, to be coupled in close contact with each other between the upper and lower housings 40 and 50, the outermost heat-radiating fin modules 20 are mounted with side frames 60 on left-hand and right-hand outer sides thereof. In detail, the side frames 60 are curved inwards, and are coupled to the upper and lower housings 40 and 50. The PTC rods 10, heat-radiating fin modules 20 and cathode terminals 30 are coupled in close contact with one another by means of an elastic contact force of the curved side frames 60. This coupling allows elasticity and heat to be efficiently transferred among the PTC rods 10, heat-radiating fin modules 20 and cathode terminals 30. As a result, the entire structure of the PTC heater is formed.
Meanwhile, as illustrated in FIG. 1, each heat-radiating fin module 20 is for increasing efficiency with which each PTC rod 10 exchanges heat with air, and includes a heat-radiating fin 21 corrugated in a lengthwise direction so as to increase a contact area with air, a case 22 fixedly holding the heat-radiating fin 21, and a cover 23 fastened to the case 22 by bolts 24 so as to close an open side of the case 22. Here, in order to fix the heat-radiating fin 21 as a component for substantially improving the heat-exchange efficiency, the case 22 and cover 23 are separately prepared such that the heat-radiating fin 21 is prevented from being separated or moving from the PTC rod 10.
Thus, each heat-radiating fin module 20 is complicated when manufactured, and increases the number of parts, because the case 22 and cover 23 are additionally required to fix the heat-radiating fin 21. In order to solve this problem, the method of manufacturing the PTC heater is changed. For example, as illustrated in FIG. 2, a method of manufacturing each heat-radiating fin module 20′ using a simple fin guide 25 and heat-radiating fin 21 has been developed. In this method, the heat-radiating fin module 20′ also requires the fin guide 25 to fix the heat-radiating fin 21, and the fin guide 25 is configured so that opposite edges thereof are bent into flanges 25a. Although this structure can be regarded to be simpler than that of FIG. 1, the heat-radiating fin module 20′ still suffers from a complicated manufacturing process and a number of parts.
Further, since this heat-radiating fin module 20 or 20′ is configured so that the separate part, i.e. the case 22 or the fin guide 25, is interposed between the heat-radiating fin 21 and the PTC rod 10, heat transfer efficiency with which the heat emitted from the PTC rod 10 is transferred to the heat-radiating fin 21 is lowered. Furthermore, since the contact between the PTC rod 10 and the heat-radiating fin 21 is caused by the elastic contact force of the side frames 60, the contact is dependent upon surface roughness of the PTC rod 10 and/or the heat-radiating fin 21, and thus the heat transfer efficiency is lowered.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.